Question

Show that the following points are collinear.

(3, 7), (6, 5) and (15, -1)

Answer 1

for collinearly of point $A,B,C$

Slope of $AB=$Slope of $BC$

$A(3,7),B(6,5),C(15,-1)$

Slope of $(x_1,y_1)(x_2,y_2)$

$=\frac{y_2-y_1}{x_2-x_1}$

$m_{AB}=\frac{5-7}{6-3}=\frac{-2}{3}$

$m_{BC}=\frac{-1-5}{15-6}=\frac{-6}{9}=\frac{-2}{3}$

Hence they are collinear.